KR20230111969A - Flexible printed circuit board, cof module and electronic device comprising the same - Google Patents

Abstract

A flexible printed circuit board according to an embodiment includes a circuit pattern disposed on the substrate; a protective layer on the circuit pattern, the circuit pattern includes a plurality of first circuit patterns and a plurality of second circuit patterns, the plurality of first circuit patterns include a first pattern part and a second pattern part having a minimum length among the plurality of first circuit patterns, the first pattern part includes a first side surface and a second side surface, the first pattern part includes a first bent part and a second bent part, and the first bent part and the second pattern part have a minimum length. A sum of the length of the first side surface between the bent parts and the length of the second side surface between the first bent part and the second bent part is 90 μm or more.

Description

Flexible printed circuit board, COF module and electronic device including the same

The embodiment relates to a flexible printed circuit board, a COF module, and an electronic device including the same. In detail, the flexible printed circuit board may be a flexible printed circuit board for COF.

Recently, various electronic products are becoming thinner, smaller, and lighter. Accordingly, various studies are being conducted to mount semiconductor chips at a high density in a narrow area of an electronic product.

Among them, the COF (Chip On Film) method can be applied to a flexible display because it uses a flexible substrate. That is, the COF method is spotlighted in that it can be applied to various wearable electronic devices. In addition, since the COF method can implement a fine pitch, it can be used to implement a high-resolution display according to an increase in the number of pixels.

COF (Chip On Film) is a method of mounting a semiconductor chip on a flexible printed circuit board in the form of a thin film. For example, the semiconductor chip may be an integrated circuit (IC) chip or a large scale integrated circuit (LSI) chip.

Meanwhile, the chip may be connected to an external PCB and display panel through a circuit pattern. For example, pad parts may be disposed at one end and the other end of the circuit pattern, one pad part may be electrically connected to a terminal of the chip, and the other pad part may be connected to terminals of the PCB and display panel. Accordingly, the chip, the PCB, and the display panel are electrically connected through the COF, and a signal can be transferred to the display panel through the circuit pattern.

As explained earlier. Since the COF (Chip On Film) flexible printed circuit board is applied to a flexible display, the C flexible printed circuit board can be bent in one direction.

Therefore, when the flexible printed circuit board is bent, cracks or peeling may occur in the circuit pattern located in the bent region, and electrical characteristics of the flexible printed circuit board may be deteriorated.

Accordingly, a flexible printed circuit board having a new structure capable of solving the above problems is required.

Embodiments are intended to provide a flexible printed circuit board having improved reliability.

A flexible printed circuit board according to an embodiment includes a circuit pattern disposed on the substrate; a protective layer on the circuit pattern, the circuit pattern includes a plurality of first circuit patterns and a plurality of second circuit patterns, the plurality of first circuit patterns include a first pattern part and a second pattern part having a minimum length among the plurality of first circuit patterns, the first pattern part includes a first side surface and a second side surface, the first pattern part includes a first bent part and a second bent part, and the first bent part and the second pattern part have a minimum length. A sum of the length of the first side surface between the bent parts and the length of the second side surface between the first bent part and the second bent part is 90 μm or more.

In the flexible printed circuit board according to the embodiment, the length of the first side surface between the first bent part and the second bent part is different from the length of the second side surface between the first bent part and the second bent part.

In the flexible printed circuit board according to the embodiment, the length of the second side surface between the first bent part and the second bent part is 80% to 95% of the length of the first side surface between the first bent part and the second bent part.

In the flexible printed circuit board according to the embodiment, the width of the first pattern portion changes while extending from the first bent portion to the second bent portion.

In the flexible printed circuit board according to the embodiment, a curvature of the first bent portion is different from a curvature of the second bent portion.

In the flexible printed circuit board according to the embodiment, the first bent part of the first side and the first bent part of the second side face each other in a direction different from the width direction of the first pattern part, and the second bent part of the second side and the second bent part of the second side face each other in a direction different from the width direction of the first pattern part.

In the flexible printed circuit board according to the embodiment, the first side surface is disposed closer to the central portion of the substrate than the second side surface, and the first side surface is disposed concavely toward the second side surface.

In the flexible printed circuit board according to the embodiment, a first side surface of the first pattern portion defines a virtual line extending from the first bent portion toward the second bent portion, and the distance between the first side surface and the virtual line increases and then decreases.

In the flexible printed circuit board according to the embodiment, a gap between the first pattern part and the second pattern part includes a region in which a width increases while extending from the first bent part toward the second bent part.

In the flexible printed circuit board according to the embodiment, the second pattern portion includes a third side surface and a fourth side surface, the first side surface is disposed closer to the central portion of the substrate than the second side surface is disposed, the third side surface is disposed closer to the central portion of the substrate than the fourth side surface, and the second pattern portion includes a third bent portion and a fourth bent portion, and the distance between the first side surface and the third side surface is the same as the first bent portion. It includes an area that increases while extending in the direction of the second bent portion.

In the flexible printed circuit board according to the embodiment, the distance between the first pattern part and the second pattern part, the first side surface between the first bent part and the second bent part and the third side The maximum distance is greater than the distance between the pad part of the first pattern part and the pad part of the second pattern part.

A flexible printed circuit board according to an embodiment includes a region in which the sum of side lengths of circuit patterns increases.

In detail, the pattern portion having the minimum length among the circuit patterns of the flexible printed circuit board may have a size in which the sum of the lengths of both sides is 90 μm or more.

Accordingly, when the flexible printed circuit board is bent, the rigidity of the pattern portion vulnerable to the stress caused by the bending may be secured. That is, as the length of the side surface of the pattern part is increased, the length of the stress moving to the side surface of the pattern part may be reduced.

Accordingly, it is possible to prevent cracks from being generated in the pattern portion of the first circuit pattern due to stress caused by the bending.

In addition, by making the distance between pattern parts having the minimum length larger than the distance between pattern parts having other lengths, it is possible to prevent a short circuit from occurring between adjacent pattern parts.

That is, the flexible active circuit board according to the embodiment may have improved reliability and driving characteristics.

1 is a top view of a flexible printed circuit board according to an embodiment.
2 and 3 are cross-sectional views of an area AA′ of FIG. 1 .
FIG. 4 is a cross-sectional view of a region BB′ of FIG. 1 .
FIG. 5 is an enlarged view showing an enlarged area A of FIG. 1 .
6 is a top view of a COF module according to an embodiment.
7 is a cross-sectional view showing a connection relationship of a COF module including a flexible printed circuit board according to an embodiment.
8 to 10 are views of an electronic device including a flexible printed circuit board according to an embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical idea of the present invention is not limited to some of the described embodiments, but can be implemented in various different forms, and within the scope of the technical idea of the present invention, one or more of the components among the embodiments can be selectively combined, replaced, and used.

In addition, the terms (including technical and scientific terms) used in the embodiments of the present invention, unless specifically defined and described, can be interpreted in a meaning that can be generally understood by those skilled in the art to which the present invention belongs, and commonly used terms, such as terms defined in a dictionary, will be able to interpret their meaning in consideration of the contextual meaning of the related art.

Also, terms used in the embodiments of the present invention are for describing the embodiments and are not intended to limit the present invention. In this specification, the singular form may also include the plural form unless otherwise specified in the phrase, and when described as “at least one (or more than one) of A and (and) B and C” A, B, C may include one or more of all combinations that can be combined.

Also, terms such as first, second, A, B, (a), and (b) may be used to describe components of an embodiment of the present invention. These terms are only used to distinguish the component from other components, and the term is not limited to the nature, order, or order of the corresponding component.

In addition, when a component is described as being 'connected', 'coupled', or 'connected' to another component, the component may be directly connected, coupled, or connected to the other component, as well as a case of being 'connected', 'coupled', or 'connected' due to another component between the component and the other component.

In addition, when it is described as being formed or disposed "upper (above) or lower (below)" of each component, the upper (above) or lower (below) includes not only a case where two components are in direct contact with each other, but also a case where one or more other components are formed or disposed between the two components.

In addition, when expressed as “up (up) or down (down)”, it may include the meaning of not only the upward direction but also the downward direction based on one component.

Hereinafter, a flexible printed circuit board according to an embodiment, a COF module, and an electronic device including the same will be described with reference to the drawings.

1 is a top view of a flexible printed circuit board according to an embodiment.

Referring to FIG. 1 , a flexible printed circuit board 1000 according to an embodiment may include a substrate 100 and a circuit pattern 200 disposed on the substrate 100 .

The substrate 100 may include a flexible substrate. For example, the substrate 100 may be a polyimide (PI) substrate. However, the embodiment is not limited thereto, and the substrate 100 may include a polymer material such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). Accordingly, the flexible printed circuit board including the substrate 100 can be used in various electronic devices equipped with curved display devices. For example, as the flexible printed circuit board including the substrate 100 has excellent flexible characteristics, it may be suitable for mounting a semiconductor chip of a wearable electronic device.

The substrate 100 may have a thickness of 20 μm to 100 μm. For example, the substrate 100 may have a thickness of 25 μm to 50 μm. For example, the substrate 100 may have a thickness of 30 μm to 40 μm. When the thickness of the base material 100 exceeds 100 μm, the overall thickness of the flexible printed circuit board may increase, and as a result, flexible characteristics may be deteriorated. In addition, when the substrate 100 has a thickness of less than 20 μm, it may be vulnerable to heat/pressure applied to the substrate 100 in a chip mounting process.

The substrate 100 may include an effective area UA and an ineffective area UA. For example, the effective area AA may be a central area of the substrate 100 and the non-effective area UA may be an edge area of the substrate 100 . That is, the non-effective area UA may be disposed surrounding the effective area AA.

The effective area AA may include a chip mounting area CA. In detail, the effective area AA may include a chip mounting area CA in which a chip C connected to the circuit pattern is mounted.

Also, circuit patterns 210 and 220 may be disposed on the effective area AA. In detail, a plurality of circuit patterns spaced apart from each other and extending in multiple directions may be disposed in the effective area AA.

The effective area AA may be an area actually used in the flexible printed circuit board 1000 . That is, when the flexible printed circuit board comes into contact with another panel, etc., the effective area AA may be an area that is in contact with each other.

The circuit pattern may not be disposed in the non-effective area UA. That is, depending on whether or not the circuit pattern is disposed, the effective area AA and the non-active area UA may be distinguished.

The non-effective area UA may include a plurality of holes. In detail, the ineffective area UA may include a plurality of sprocket holes H. Due to the sprocket hole H, the flexible printed circuit board may be wound or unwound through the sprocket hole in a roll-to-roll manner.

The non-effective area UA may be an area not actually used in the flexible printed circuit board 1000 . That is, the non-effective area UA may be removed when the flexible printed circuit board comes into contact with another panel or the like.

In detail, the flexible printed circuit board 1000 is processed into a COF module after cutting the cutting line CL defined by the boundary between the non-active area UA where the sprocket hole H is formed and the effective area AA, and can be mounted in various electronic devices.

The circuit pattern may include a wiring part and a pad part. Also, a plurality of circuit patterns may be disposed in the effective area AA. In detail, a first circuit pattern 210 and a second circuit pattern 220 may be disposed in the effective area AA.

Referring to FIGS. 1 to 3 , the first circuit pattern 210 may include a first wiring part 211 , a first pad part 212a and a second pad part 212b. In detail, the first circuit pattern 210 is disposed between the first pad portion 212a disposed inside the chip mounting area CA, the second pad portion 212b disposed outside the chip mounting area CA, and disposed between the first pad portion 212a and the second pad portion 212b, and connected to the first pad portion 212a and the second pad portion 212b A first wiring part 211 may be included.

The first wiring part 211, the first pad part 212a, and the second pad part 212b may be integrally formed.

In addition, the first wiring part 211 may extend in the first direction 1D with respect to the chip mounting area CA.

The first pad part 212a may be electrically connected to a chip disposed in the chip mounting area. Also, the second pad part 212b may be electrically connected to another display panel. Also, the first wiring part 211 may transmit a signal between the chip and the display panel.

A protective layer 300 may be disposed on the first circuit pattern 210 . In detail, the protective layer 300 may be disposed on the first wiring part 211 . The protective layer 300 may be disposed while surrounding the first wiring part 211 . In addition, the protective layer 300 may not be disposed on the first pad part 212a and the second pad part 212b.

That is, the first wiring part 211 is disposed below the protective layer 300, and the protective layer 300 is not disposed on the first pad part 212a and the second pad part 212b. It can be exposed to the outside.

Also, referring to FIGS. 1 and 4 , the second circuit pattern 220 may include a second wiring part 221 , a third pad part 222a and a fourth pad part 222b. In detail, the second circuit pattern 220 is disposed between the third pad portion 222a disposed inside the chip mounting area CA, the fourth pad portion 222b disposed outside the chip mounting area CA, and between the third pad portion 222a and the fourth pad portion 222b, and connected to the third pad portion 222a and the fourth pad portion 222b A second wiring part 221 may be included.

The second wiring part 221, the third pad part 222a, and the fourth pad part 222b may be integrally formed.

Also, the second wiring part 221 may be disposed extending in the A2 direction A2 based on the chip mounting area CA. In detail, the second wiring part 221 may be disposed extending in a second direction 2D opposite to the first direction 1D.

The third pad part 222a may be electrically connected to a chip disposed in the chip mounting area. Also, the fourth pad part 222b may be electrically connected to the printed circuit board. Also, the second wiring part 221 may transfer a signal between the chip and the printed circuit board.

A protective layer 300 may be disposed on the second circuit pattern 220 . In detail, the protective layer 300 may be disposed on the second wiring part 221 . The protective layer 300 may be disposed while surrounding the second wiring part 221 . In addition, the protective layer 300 may not be disposed on the third pad portion 222a and the fourth pad portion 222b.

That is, the second wiring part 221 is disposed under the protective layer 300, and the protective layer 300 is not disposed on the third pad part 222a and the fourth pad part 222b. Can be exposed to the outside.

The first circuit pattern 210 and the second circuit pattern 220 may include a metal material having excellent electrical conductivity. In detail, the first circuit pattern 210 and the second circuit pattern 220 may include copper (Cu). However, the embodiment is not limited thereto, and the first circuit pattern 210 and the second circuit pattern 220 are made of copper (Cu), aluminum (Al), chromium (Cr), nickel (Ni), silver (Ag), and molybdenum (Mo). Of course, it may include at least one metal selected from among gold (Au), titanium (Ti), and alloys thereof.

Hereinafter, the layer structure of the circuit pattern of the flexible printed circuit board according to the embodiment will be described with reference to FIGS. 2 and 3 . 2 and 3 focus on the first circuit pattern 210, but the embodiment is not limited thereto, and the description of the layer structure described in FIGS. 2 and 3 can be equally applied to the second circuit pattern 220.

Referring to FIG. 2 , the first circuit pattern 210 may be formed in multiple layers. In detail, the first wire part 211 and the first pad part 212a may include a first metal layer 201 and a second metal layer 202 . Also, although not shown in FIG. 3 . The second pad part 212b may also include the first metal layer 201 and the second metal layer 202.

The first metal layer 201 may be a seed layer of the first circuit pattern 210 . In detail, the first metal layer 201 may be a seed layer formed on the substrate 100 through electroless plating using a metal material such as copper (Cu).

Also, the second metal layer 202 may be a plating layer. In detail, the second metal layer 202 may be a plating layer formed by electroplating using the first metal layer 201 as a seed layer.

A thickness of the first metal layer 201 may be smaller than a thickness of the second metal layer 202 .

For example, the thickness of the first metal layer 201 may be 0.7 μm to 2 μm, and the thickness of the second metal layer 202 may be 10 μm to 25 μm.

The first metal layer 201 and the second metal layer 202 may include the same metal material. For example, the first metal layer 201 and the second metal layer 202 may include copper (Cu).

In addition, a bonding layer 203 may be disposed on the second metal layer 201 . In detail, the bonding layer 203 may be disposed on side surfaces of the first metal layer 201 and the second metal layer 202 and on an upper surface of the second metal layer 202 . That is, the bonding layer 203 may be disposed while surrounding the first metal layer 201 and the second metal layer 202 .

The bonding layer 203 may include metal. In detail, the bonding layer 203 may include tin (Sn).

The bonding layer 203 may be formed to a thickness of 0.3 μm to 0.7 μm. The bonding layer 203 may have a higher tin content while extending from a lower surface where the bonding layer 203 and the second metal layer 202 come into contact with each other in a direction toward an upper surface.

That is, since the bonding layer 203 is disposed in contact with the second metal layer 202, the content of tin may increase and the content of copper may decrease from the lower surface to the upper surface of the bonding layer 203.

Accordingly, only pure tin may remain in the thickness range of 0.1 μm to 0.3 μm on the upper surface of the bonding layer 203 .

The bonding layer 203 can easily bond the chip, the printed circuit board, and the terminals of the display panel to the first pad part and the second pad part through heat and pressure. That is, when heat and pressure are applied to the first pad part and the second pad part, the upper surface where pure tin remains in the bonding layer is melted and easily adhered to the terminals of the chip, the printed circuit board, and the display panel.

Accordingly, the bonding layer 203 may be part of the first pad portion without being separated from the first pad portion 212a.

The first circuit pattern 210 may have a thickness of 2 μm to 25 μm. For example, the first circuit pattern 210 may be disposed to a thickness of 5 μm to 20 μm. For example, the first circuit pattern 210 may be disposed to a thickness of 7 μm to 15 μm.

Since the first circuit pattern 210 undergoes a process of etching the first metal layer 201 by flash etching to separate circuit patterns during the manufacturing process, the first circuit pattern 211 and the second circuit pattern 220 finally manufactured have a thickness of the first metal layer 201, the second metal layer 202, and the bonding layer 203 formed during the manufacturing process. may be less than the sum.

When the thickness of the first circuit pattern 210 and the second circuit pattern 220 is less than 2 μm, the resistance of the first circuit pattern 210 and the second circuit pattern 220 may increase. When the thickness of the first circuit pattern 210 and the second circuit pattern 220 exceeds 25 μm, it may be difficult to implement a fine pattern.

Meanwhile, a buffer layer 205 may be further disposed between the substrate 100 and the first circuit pattern 210 and the second circuit pattern 220 . The buffer layer 205 may improve adhesion between the substrate 100 that is a heterogeneous material and the first circuit pattern 210 and the second circuit pattern 220 .

The buffer layer 205 may be formed in multiple layers. In detail, a first buffer layer 205a and a second buffer layer 205b on the first buffer layer 205a may be disposed on the substrate 100 . Accordingly, the first buffer layer 205a may contact the substrate 100 and the second buffer layer 205b may contact the first circuit pattern 201 .

The first buffer layer 205a may include a material having good adhesion to the substrate 100 . For example, the first buffer layer 205a may include nickel (Ni). In addition, the second buffer layer 205b may include a material having good adhesion to the first circuit pattern 210 . For example, the second buffer layer 205b may include chromium (Cr).

The buffer layer 205 including the first buffer layer 205a and the second buffer layer 205b may have a thin film thickness in nanometers. For example, the buffer layer 205 may have a thickness of 20 nm or less.

Since the buffer layer 205 can improve the adhesion between the base material 100 that is a heterogeneous material and the first circuit pattern 210 , film separation of the first circuit pattern 201 can be prevented.

Meanwhile, referring to FIG. 3 , the bonding layer 203 may include a first bonding layer 203a and a second bonding layer 203b.

In detail, the first bonding layer 203a may be disposed on the first wiring part 211 and the first pad part 212a. Also, although not shown in the drawing, the first bonding layer 203a may also be disposed on the second pad part 212b. That is, the first bonding layer 203a may be disposed on the first circuit pattern 210 .

In addition, the second bonding layer 203b may be disposed only on the first pad part 212a and the second pad part 212b. That is, the first wiring part 211, the first pad part 212a, and the second pad part 212b may have different layer structures due to the second bonding layer 203b.

The first bonding layer 203a and the second bonding layer 203b may include metal. In detail, the first bonding layer 203a and the second bonding layer 203b may include tin (Sn).

The first bonding layer 203a and the second bonding layer 203b may have different thicknesses. In detail, the thickness of the second bonding layer 203b may be greater than that of the first bonding layer 203a.

For example, the first bonding layer 203a may have a thickness of 0.02 μm to 0.06 μm, and the second bonding layer 203b may have a thickness of 0.2 μm to 0.6 μm.

When the bonding layer is thickly disposed between the protective layer 300 and the first wiring part 211, cracks may occur when the flexible printed circuit board is bent. Accordingly, since the first bonding layer 231 between the protective layer 300 and the first wiring part 211 is formed with a thin film thickness, it is possible to prevent cracks from occurring when the flexible printed circuit board is bent.

In addition, the second bonding layer 203b may have a higher tin content while extending from a lower surface where the second bonding layer 203b and the first bonding layer 203a contact each other toward an upper surface.

That is, the content of tin in the second bonding layer 203b may increase and the content of copper may decrease from the lower surface to the upper surface of the second bonding layer 203b.

Accordingly, only pure tin may remain in the thickness range of 0.1 μm to 0.3 μm on the upper surface of the second bonding layer 203b.

By means of the second bonding layer 203b, terminals of the chip, the printed circuit board, and the display panel may be easily bonded to the first pad part and the second pad part through heat and pressure. That is, when heat and pressure are applied to the first pad part and the second pad part, the upper surface where pure tin remains in the bonding layer is melted and easily adhered to the terminals of the chip, the printed circuit board, and the display panel.

Accordingly, the first bonding layer 203a and the second bonding layer 203b may be part of the first pad unit without being separated from the first pad unit 212a.

Meanwhile, the protective layer 300 may be disposed on wiring parts of the first circuit pattern 210 and the second circuit pattern 220 . In detail, the protective layer 300 may be disposed while surrounding the first wiring part 211 and the second wiring part 221 . That is, the protective layer 300 may be disposed on the first circuit pattern 210 and the second circuit pattern 220 except for the first pad part, the second pad part, the third pad part, and the fourth pad part.

The protective layer 300 may include solder paste. For example, the protective layer 300 may include a solder paste containing a thermosetting resin, a thermoplastic resin, a filler, a curing agent, or a curing accelerator.

Meanwhile, in the foregoing description, it has been described that the first circuit pattern 210 and the second circuit pattern 220 are disposed on the same surface of the substrate 100, but the embodiment is not limited thereto.

In detail, the first circuit pattern 210 and the second circuit pattern 220 may be disposed on the other side of the substrate 100 . For example, the first circuit pattern 210 may be disposed on one surface of the substrate 100, and the second circuit pattern 220 may be disposed on the other surface opposite to one surface of the substrate 100.

Accordingly, the display panel may be connected to the chip on one surface of the substrate 100, and the printed circuit board may be connected to the chip on the other surface of the substrate 100 on the other surface of the substrate 100.

FIG. 5 is an enlarged view of area A of FIG. 1 .

Referring to FIGS. 1 and 5 , the first circuit pattern 210 may include a plurality of circuit patterns. The plurality of first circuit patterns 210 may be disposed extending in a plurality of directions. In detail, the first wiring part 211 of the first circuit pattern 210 may be disposed extending in a plurality of directions.

The first wiring part 211 may be disposed extending in at least one direction while being connected to the first pad part 212a and the second pad part 212b.

Accordingly, the first circuit pattern 210 may include a plurality of first circuit patterns having different lengths. That is, the first circuit pattern 210 may include a plurality of first circuit patterns having different lengths depending on the degree of bending.

The first circuit pattern 210 may include a pattern portion having a minimum length among a plurality of first circuit patterns. In detail, the first circuit pattern 210 may include a first pattern portion P1 and a second pattern portion P2 having a minimum length among a plurality of first circuit patterns.

Each of the first pattern part P1 and the second pattern part P2 may correspond to one of the plurality of first wiring parts 211 of the first circuit pattern 210 .

That is, the first pattern part P1 and the second pattern part P2 may have shorter lengths than the first wiring parts of other first circuit patterns. In addition, the lengths of the first pattern portion P1 and the second pattern portion P2 may be the same within a tolerance range.

The first pattern part P1 and the second pattern part P2 may be disposed adjacent to each other. The first pattern part P1 and the second pattern part P2 may be disposed facing each other. For example, the first pattern part P1 and the second pattern part P2 may be disposed facing each other in the longitudinal direction of the substrate 100 .

The first pattern portion P1 may include a first side surface LS1 and a second side surface LS2. The first side surface LS1 may be disposed closer to the central portion of the flexible printed circuit board than the second side surface LS2 . A distance between the first side surface LS1 and the second side surface LS2 may be defined as the width of the first pattern portion P1.

The first side surface LS1 and the second side surface LS2 may be disposed to face each other. Also, the first side surface LS1 may be disposed facing the second pattern part P2.

The first pattern portion P1 may include a first bent portion B1 and a second bent portion B2. The first bent part B1 and the second bent part B2 may be defined as points where bending of the first pattern part P1 starts. For example, the second bent part B2 is defined as a point at which the first bending of the first pattern part P1 starts from the second pad part 212b to the first pad part 212a, and the first bent part B1 is a point at which the second bending of the first pattern part P1 starts from the second pad part 212b to the first pad part 212a. can be defined as That is, the first pattern portion P1 may be bent in different directions at the first bent portion B1 and bent in different directions at the second bent portion B2.

Accordingly, the first side surface LS1 and the second side surface LS2 may include a first bent portion B1 and a second bent portion B2, respectively.

A sum of the length of the first side surface between the first bent part B1 and the second bent part B2 and the length of the second side surface between the first bent part and the second bent part may have a set range.

In detail, the sum of the length of the first side surface between the first bent part B1 and the second bent part B2 and the length of the second side surface between the first bent part and the second bent part may be 90 μm, 100 μm, or 120 μm or more.

When the sum of the lengths of the first side surface LS1 and the second side surface LS2 of the first pattern part P1 between the first bent part B1 and the second bent part B2 has the above range, cracking of the first circuit pattern 210 can be prevented.

In detail, one of the regions where the first circuit pattern 210 extends may be bent in one direction on the flexible printed circuit board. When the flexible printed circuit board is bent, stress may be generated due to the bending, and this stress may be transferred to the first circuit pattern and cracks may be generated in the first circuit pattern. In particular, the first pattern portion having the minimum length among the first circuit patterns 210 may be vulnerable to such stress.

Therefore, the flexible printed circuit board according to the embodiment forms the sum of the side lengths of the first pattern part within a set range, thereby preventing cracks in the first circuit pattern due to bending stress.

That is, the first pattern part has a plurality of bent parts, and the sum of side lengths of the first pattern part may be increased by the bent parts. Accordingly, it is possible to reduce the magnitude of stress moving along the side surface of the first pattern part. That is, since the sum of the side lengths of the first pattern part increases, the stress per length of the first pattern part decreases, and thus the magnitude of the stress applied to the first pattern part can be reduced.

Therefore, the flexible printed circuit board according to the embodiment can prevent damage to circuit patterns due to stress generated during bending, and thus can have improved reliability.

A length of the first side surface between the first bent part and the second bent part may be different from a length of the second side surface between the first bent part and the second bent part. In detail, the curvature of the first side surface LS1 and the curvature of the second side surface LS2 may be different. Accordingly, as for the length of the first side surface between the first bent part and the second bent part, any one of the lengths of the second side surface between the first bent part and the second bent part may be greater than the other length.

In addition, the difference between the length of the first side surface between the first bent part and the second bent part and the length of the second side surface between the first bent part and the second bent part may be formed within a set range.

In detail, when the length of the first side surface between the first bent part and the second bent part is greater than the length of the second side surface between the first bent part and the second bent part, the first bent part and the second bent part. The length of the second side surface between the bent part may be 80% or more of the length of the first side surface between the first bent part and the second bent part.

In detail, the length of the second side surface between the first bent part and the second bent part may be 80% to 95% of the length of the first side surface between the first bent part and the second bent part.

Implementing the length of the second side surface between the first bent part and the second bent part to exceed 95% of the length of the first side surface between the first bent part and the second bent part may be difficult to implement in terms of process. In addition, when the length of the second side surface between the first bent part and the second bent part is less than 80% of the length of the first side surface between the first bent part and the second bent part, the first side surface (LS1) And the magnitude of the stress per length applied to the second side surface (LS2) is non-uniform, and cracks may occur in the first pattern part.

The width of the first pattern portion P1 may vary while extending in one direction. In detail, the width of the first pattern portion P1 may change while extending from the first bent portion B1 toward the second bent portion B2. For example, the first pattern portion P1 may include a widened area extending from the first bent portion B1 toward the second bent portion B2. In addition, the first pattern portion P1 may include a narrower area extending from the first bent portion B1 toward the second bent portion B2.

Each of the first side surface LS1 and the second side surface LS2 may include a bent portion. The first bent part of the first side surface LS1 and the first bent part of the second side surface LS2 may be displaced from each other.

In detail, the first bent part of the first side surface LS1 and the first bent part of the second side surface LS2 may be disposed to face each other in a direction different from the width direction of the first pattern part P1.

Also, the second bent part of the first side surface LS1 and the second bent part of the second side surface LS2 may be disposed to face each other in a direction different from the width direction of the first pattern part P1.

As a result, the shape of the first pattern portion P1 can be transformed into more diverse shapes, and the width of the first pattern portion P1 can be transformed into more diverse sizes.

Therefore, it is possible to minimize the occurrence of cracks in the first pattern portion P1 due to the tolerance of the bending position of the flexible printed circuit board.

The first pattern portion P1 may have a concave shape. In detail, the first side surface LS1 of the first pattern part P1 may be concavely disposed in the direction of the second side surface LS2.

In addition, the first pattern portion P1 may define a virtual line extending from the first bent portion. In detail, an imaginary line VL extending from the first bent portion toward the second bent portion may be defined on the first side surface LS1 of the first pattern portion P1.

A distance between the first side surface LS1 and the virtual line VL may be different for each location. In detail, the first pattern part P1 may include a region in which a distance between the first side surface LS1 and the virtual line VL increases. Also, the first pattern portion P1 may include a region in which a distance between the first side surface LS1 and the virtual line VL decreases.

That is, the distance between the first side surface LS1 and the imaginary line VL of the first pattern part P1 may increase and then decrease.

Accordingly, a distance between the first pattern part and the adjacent pattern part may be increased in a region where the width of the first pattern part including the bent part is changed, thereby preventing the pattern parts from shorting each other.

Similar to the first pattern portion P1 described above, the second pattern portion P2 may include a plurality of side surfaces and bent portions.

In detail, the second pattern portion P2 may include a third side surface LS3 and a fourth side surface LS4. The third side surface LS3 may be disposed closer to the central portion of the flexible printed circuit board than the fourth side surface LS4 . A distance between the third side surface LS3 and the fourth side surface LS4 may be defined as the width of the second pattern part P2 .

The third side surface LS3 and the fourth side surface LS4 may be disposed to face each other. Also, the third side surface LS3 may be disposed facing the first pattern part P1. That is, the third side surface LS3 may be disposed facing the first side surface LS1 of the first pattern part P1.

The second pattern portion P2 may include a third bent portion B3 and a fourth bent portion B4. The third bent part B3 and the fourth bent part B4 may be defined as points where bending of the second pattern part P2 starts. For example, the fourth bent part B4 is defined as a point where the first bending starts from the second pad part 212b of the second pattern part P2 to the first pad part 212a, and the third bent part B3 is a point where bending starts second from the second pad part 212b of the second pattern part P2 to the first pad part 212a. can be defined as

That is, the second pattern portion P2 may be bent in different directions at the third bent portion B3 and bent in different directions at the fourth bent portion B4.

Accordingly, the third side surface LS3 and the fourth side surface LS4 may include a third bent portion B3 and a fourth bent portion B4, respectively.

The sum of the length of the first side surface between the third bent part B3 and the fourth bent part B4 and the length of the second side surface between the third bent part and the fourth bent part, the difference between the length of the third side surface between the third bent part and the fourth bent part and the length of the fourth side surface between the third bent part and the fourth bent part, a change in the width of the second pattern part, the second pattern Since the shape of the portion and the misaligned arrangement of the third bent portion and the fourth bent portion are the same as or similar to those of the first pattern portion described above, the following description is omitted.

The first pattern part P1 and the second pattern part P2 are spaced apart from each other. Accordingly, the distance d between the first pattern part P1 and the second pattern part P2 may be defined as the distance between the first side surface LS1 of the first pattern part P1 and the third side surface LS3 of the second pattern part P2.

A distance between the first pattern part P1 and the second pattern part P2 may be varied while extending in one direction. In detail, the distance between the first pattern part P1 and the second pattern part P2 may change while extending in one direction.

For example, the distance between the first side surface LS1 and the third side surface LS3 extends from the first bent part toward the second bent part or from the third bent part toward the fourth bent part. It may include an area that increases.

Alternatively, the distance between the first side surface LS1 and the third side surface LS3 increases while extending from the first bent part toward the second bent part or from the third bent part toward the fourth bent part. It may include a region that decreases.

Also, the maximum distance between the first side surface LS1 and the third side surface LS3 may be greater than the maximum distance of other areas. In detail, the maximum distance between the first side surface LS1 and the third side surface LS3 may be greater than the maximum distance other than between the first side surface and the third side surface.

For example, the maximum distance between the first side surface LS1 and the third side surface LS3 between the first bent part and the second bent part may be greater than the distance between the second pad part of the first pattern part P1 and the second pad part of the second pattern part P2.

That is, the size of the distance between the first pattern part P1 and the second pattern part P2 in an area including the bent parts may be greater than that in other areas.

Accordingly, it is possible to prevent a short circuit from occurring due to the first pattern part and the second pattern part being disposed adjacent to each other by the bent parts.

A flexible printed circuit board according to an embodiment includes a region in which the sum of side lengths of circuit patterns increases.

In detail, the pattern portion having the minimum length among the circuit patterns of the flexible printed circuit board may have a size in which the sum of the lengths of both sides is 90 μm or more.

Accordingly, when the flexible printed circuit board is bent, the rigidity of the pattern portion vulnerable to the stress caused by the bending may be secured. That is, as the length of the side surface of the pattern part is increased, the length of the stress moving to the side surface of the pattern part may be reduced.

Accordingly, it is possible to prevent cracks from being generated in the pattern portion of the first circuit pattern due to stress caused by the bending.

In addition, by making the distance between pattern parts having the minimum length larger than the distance between pattern parts having other lengths, it is possible to prevent a short circuit from occurring between adjacent pattern parts.

That is, the flexible active circuit board according to the embodiment may have improved reliability and driving characteristics.

6 is a top view of a COF module according to an embodiment.

Referring to FIG. 6 , the COF module according to the embodiment includes the flexible printed circuit board described above and may include a chip C disposed in the chip mounting area CA of the flexible printed circuit board 1000 .

In addition, the flexible printed circuit board 1000 may include the protective layer 300 described above.

Meanwhile, the COF module may be manufactured by cutting the second area 2A of the flexible printed circuit board 1000 and mounting the chip C thereon. In detail, after cutting the cutting line CL of FIG. 1, the driving chip electrically connected to the first circuit pattern and the second circuit pattern is disposed in the chip mounting area of the flexible printed circuit board, and the driving chip is mounted. The COF module 2000 can be manufactured.

For example, after testing the driving characteristics of the flexible printed circuit board through a wire and a pad part disposed outside the cutting line CL of the flexible printed circuit board, the flexible printed circuit board can be cut along the cutting line CL.

The COF module may be positioned between the display panel and the substrate to connect electrical signals.

That is, pad portions of the first circuit pattern and the second circuit pattern exposed without the protective layer 300 may be connected to the display panel, the printed circuit board, and the chip in the chip mounting area.

Referring to FIG. 7 , one end of a COF module 2000 including a flexible printed circuit board according to the embodiment may be connected to the display panel 3000, and the other end opposite to the one end may be connected to the substrate 4000.

For example, one end of the COF module 2000 including the flexible printed circuit board according to the embodiment is electrically connected as it contacts the display panel 3000, and the other end opposite to the one end is the printed circuit board 4000. It can be electrically connected as it contacts. Here, contact may mean direct contact. Alternatively, it may mean contact with an anisotropic conductive film (ACF) interposed therebetween.

For example, the anisotropic conductive film may be disposed between the COF module 2000 and the printed circuit board 4000 . The COF module 2000 and the printed circuit board 4000 may be electrically connected while being adhered to each other by the anisotropic conductive film. The anisotropic conductive film may be a resin in which conductive particles are dispersed. Therefore, electrical signals connected by the printed circuit board 4000 can be transmitted to the COF module 2000 through the conductive particles included in the anisotropic conductive film.

Since the COF module 1000 includes a flexible substrate, it may have a rigid or bent shape between the display panel 3000 and the printed circuit board 4000 .

Since the COF module 2000 can connect the display panel 3000 and the printed circuit board 4000 facing each other in a bent form, the thickness of the electronic device can be reduced and the degree of freedom in design can be improved. In addition, since the COF module 2000 including the flexible substrate may not break wires even in a bent shape, reliability of an electronic device including the COF module may be improved.

Since the COF module is flexible, it can be used in various electronic devices.

For example, referring to FIG. 8 , the COF module may be included in a bendable flexible touch window. Therefore, a touch device device including this may be a flexible touch device device. Therefore, the user can bend or bend it by hand. Such a flexible touch window may be applied to a wearable touch or the like.

Referring to FIG. 9 , the COF module may be included in various wearable touch devices including curved displays. Therefore, the electronic device including the COF module can be slimmed down or lightened in weight.

Referring to FIG. 10 , the COF module may be used in various electronic devices having a display part such as a TV, a monitor, and a laptop computer. In this case, the COF module may also be used in an electronic device having a curved display portion.

However, the embodiment is not limited thereto, and the COF flexible printed circuit board and the COF module processed therefrom can be used in various electronic devices.

The features, structures, effects, etc. described in the foregoing embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, etc. illustrated in each embodiment can be combined or modified with respect to other embodiments by those skilled in the art in the field to which the embodiments belong. Therefore, contents related to these combinations and variations should be construed as being included in the scope of the present invention.

In addition, although the embodiments have been described above, these are merely examples and do not limit the present invention, and those skilled in the art to which the present invention belongs will be able to know that various modifications and applications not exemplified above are possible without departing from the essential characteristics of the present embodiment. For example, each component specifically shown in the embodiments can be modified and implemented. And differences related to these variations and applications should be construed as being included in the scope of the present invention as defined in the appended claims.

Claims (13)

write;
a circuit pattern disposed on the substrate;
a protective layer on the circuit pattern;
The circuit pattern includes a plurality of first circuit patterns and a plurality of second circuit patterns,
The plurality of first circuit patterns include a first pattern portion and a second pattern portion having a minimum length among the plurality of first circuit patterns;
The first pattern part includes a first side and a second side,
The first pattern part includes a first bent part and a second bent part,
The flexible printed circuit board of claim 1 , wherein a sum of a length of a first side surface between the first bent part and the second bent part and a length of a second side surface between the first bent part and the second bent part is 90 μm or more. According to claim 1,
A length of the first side surface between the first bent part and the second bent part is different from a length of the second side surface between the first bent part and the second bent part. According to claim 1,
A length of the second side surface between the first bent part and the second bent part is 80% to 95% of the length of the first side surface between the first bent part and the second bent part. According to claim 1,
The flexible printed circuit board of claim 1 , wherein a width of the first pattern portion changes while extending from the first bent portion to the second bent portion. According to claim 1,
A curvature of the first bent portion is different from a curvature of the second bent portion. According to claim 1,
The first bent portion of the first side and the first bent portion of the second side face each other in a direction different from the width direction of the first pattern portion,
The flexible printed circuit board of claim 1 , wherein the second bent portion of the first side and the second bent portion of the second side face each other in a direction different from a width direction of the first pattern portion. According to claim 1,
The first side is disposed closer to the central portion of the substrate than the second side,
The first side surface is disposed concavely in the direction of the second side surface. According to claim 7,
The first side of the first pattern portion is defined by a virtual line extending from the first bent portion toward the second bent portion,
A flexible printed circuit board in which a distance between the first side surface and the imaginary line increases and then decreases. According to claim 1,
The flexible printed circuit board of claim 1 , wherein the gap between the first pattern portion and the second pattern portion includes a region in which a width increases while extending from the first bent portion toward the second bent portion. According to claim 1,
The second pattern part includes a third side and a fourth side,
The second pattern part includes a third bent part and a fourth bent part,
The first side surface is disposed closer to the central portion of the substrate than the second side surface,
The third side surface is disposed closer to the central portion of the substrate than the fourth side surface,
The flexible printed circuit board of claim 1 , wherein a distance between the first side surface and the third side surface increases while extending from the first bent portion toward the second bent portion. According to claim 10,
The distance between the first pattern part and the second pattern part is such that the maximum distance between the first side surface and the third side surface between the first bent part and the second bent part is greater than the distance between the pad part of the first pattern part and the pad part of the second pattern part. Flexible printed circuit board. A flexible printed circuit board according to any one of claims 1 to 11; and
A COF module including a chip disposed in the chip mounting area. COF module according to claim 12;
a display panel connected to the first circuit pattern; and
An electronic device comprising a printed circuit board connected to the second circuit pattern.

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